Dinitroarylmethine dyes as sensitizers in electrophotographic layers

ABSTRACT

Dinitroarylmethine dyes are useful for sensitizing photoconductive compositions used in electrophotographic layers. These dyes are light bleachable so that undesirable color imparted to background areas of the image-bearing element by the dyes is removable. Such bleaching increases the visual contrast of the reproduction.

United States Patent Contois 1 Mar. 7, 1972 [54] DINITROARYLMETHINE DYES AS SENSITIZERS IN ELECTROPHOTOGRAPHIC LAYERS [72] lnventor: Lawrence Edward Contois, Webster, NY.

[73] Assignee: Eastman Kodak Company, Rochester,

221 Filed: 0ct.3, 1969 211 Appl.No.: 863,691-

[52] US. Cl. ..96/l.6, 96/1.7, 96/1 R, 260/240 A, 96/27, 96/1.5, 96/89 [51] Int. Cl. ..G03g 5/06, G03g 5/08 [58] Field ofSearch ..96/l.5l.8, 152, 96/1, 143, 89; 260/240 A [56] References Cited UNITED STATES PATENTS 2,794,802 6/1957 Horwitz ..260/240A 3,169,060 2/1965 Hoegl ..96/l.6

2,953,561 9/1960 Doorebos ..260/240 A 3,507,648 4/1970 Ford et a1. ..96/1.6

OTHER PUBLICATIONS Hoegl, On Photoelectric Effects in Polymers and Their Sensitization by Dopants, March, 1965, Journal of Physical Chemistry, Vol. 69, No. 3, pp. 755- 766 Primary Examiner-George F. Lesmes Assistant Examiner-R. E. Martin AttorneyWilliam H. J. Kline, James R. Frederick and Fred L. Denson [5 7] ABSTRACT 17 Claims, No Drawings DINITROARYLMETHINE DYES AS SENSITIZERS lN ELECTROPHOTOGRAPHIC LAYERS This invention relates to electrophotography, and in particular to novel sensitized photoconductive compositions and elements having coated thereon such compositions.

The process of xerography, as disclosed by Carlson in US. Pat. No. 2,297,691, employs an electrophotographic element comprising a support material bearing a coating of a normally insulating material whose electrical resistance varies with the amount of incident actinic radiation it receives during an imagewise exposure. The element, commonly termed a photoconductive element, is first given a uniform surface charge, generally in the dark after a suitable period of dark adaptation. It is then exposed to a pattern of actinic radiation which has the effect of differentially reducing the potential of the surface charge in accordance with the relative energy contained in various parts of the radiation pattern. The differential surface charge or electrostatic charge image remaining on the electrophotographic element is then made visible by contacting the surface with a suitable electroscopic marking material. Such marking material or toner, whether contained in an insulating liquid or on a dry carrier, can be deposited on the exposed surface in accordance with either the charge pattern or the absence of charge pattern as desired. The deposited marking material may then be either permanently fixed to the surface of the sensitive element by known means such as heat, pressure, solvent vapor, or the like, or transferred to a second element to which it may similarly be fixed. Likewise, the electrostatic charge image can be transferred to a second element and developed there.

Various photoconductive insulating materials have been employed in the manufacture of electrophotographic elements. For example, vapors of selenium and vapors of selenium alloys deposited on a suitable support and particles of photoconductive zinc oxide held in a resinous, film-forming binder have found wide application in present-day document copying applications.

Since the introduction of electrophotography, a great many organic compounds have also been screened for their photoconductive properties. As a result, a very large number of organic compounds are known to possess some degree of photoconductivity. Many organic compounds have revealed a useful level of photoconduction and have been incorporated into photoconductive compositions. Optically clear organic photoconductor-containing elements having desirable electrophotographic properties can be especially useful in electrophotography. Such electrophotographic elements may be exposed through a transparent base if desired, thereby providing unusual flexibility in equipment design. Such compositions, when coated as a film or layer on a suitable support also yield an element which is reusable; that is, it can be used to form subsequent images after residual toner from prior images has been removed by transfer and/or cleaning.

Although some of the organic photoconductors comprising the materials described are inherently light sensitive, their degree of sensitivity is usually low and in the short wavelength portion of the spectrum so that it is common practice to add materials to increase the speed and to shift the sensitivity toward the longer wavelength portion of the visible spectrum. Increasing the speed and shifting the sensitivity of such systems into the visible region of the spectrum has several advantages; it makes available inexpensive and convenient light sources such as incandescent lamps; it reduces exposure time; it makes possible the recording of a wide range of colors in proper tonal relationship, and allows projection printing through various optical systems. By increasing the speed through the use of sensitizers, photoconductors which would otherwise have been unsatisfactory are useful in processes where high speeds are required such as document copying.

A primary disadvantage associated with the use of sensitizing dyes is that, because they are highly colored, they impart undesirable discoloration to the entire photoconductive element. As a result, an image developed directly on the surface of the element can be viewed only with great difficulty because of low visual contrast. Furthermore, such an element bearing a developed image is generally unsuitable for use as a master for the making of additional reproductions.

[t is therefore an object of this invention to provide novel sensitized photoconductive elements.

It is another object of this invention to provide novel sensitized photoconductive compositions.

It is a further object of this invention to provide a process for improving the visual contrast of the sensitized photoconductive elements.

These and other objects are accomplished with photoconductive compositions containing a photoconductor and a dinitroarylmethine dye as a sensitizer for the photoconductive composition. The methine dye is generally terminated by a fiveto six-membered heterocyclic nucleus containing at least one oxygen, sulfur, selenium or nitrogen atom. This terminal heterocyclic nucleus can be substituted by various groups such as alkyl, aryl, alkenyl, halogen, nitro, etc., or can have other cyclic groups fused to one side thereof. According to this invention, it has been found that when dinitroarylmethine dyes are incorporated into photoconductive compositions, an enhanced sensitization effect is realized. Photoconductive compositions which do not contain the sensitizers of this invention frequently do not produce good quality images when used in element form in an electrophotographic process.

Several advantages result from the employment of the sensitizers described herein in photoconductive compositions. Good quality images are obtainable when photoconductive compositions containing the methine dye sensitizers are coated on supports and used in electrophotographic processes. These sensitizing dyes not only spectrally sensitize the photoconductive composition but also are capable of light induced photodecomposition yielding colorless or low color by-products. Such a combination of properties is of significant value with respect to an electrophotographic element requiring additional sensitization, particularly when the element is used as the final image-bearing element. Photolytic reduction of the density in the final background area after toning permits higher viewing contrast and the ability to produce an improved second generation print.

The sensitizing dyes of this invention are rapidly photobleachable by actinic radiation such as radiation from a cool light source. Fluorescent sources and incandescent tungsten sources are substantially equally effective. Generally, a light exposure of at least l0 foot-candle-seconds is sufficient to cause substantial bleaching (i.e., an increase in transmittance of at least 25 percent). Little or no practical advantage is obtained in using light exposures in excess of 10'' foot-candle-seconds.

The preferred dinitroarylmethine-sensitizing dyes of this invention have the following formula:

hydroxypropyl, hydroxyoctyl,

e. aralkyl, e.g., benzyl, phenethyl, etc., f. alkylaminoalkyl e.g., methylaminopropyl,

methylaminoethyl, etc,, and also including dialkylaminoalkyl e.g., diethylaminoethyl, dimethylaminopropyl, dipropylamino-octyl, etc., gv arylaminoalkyl, e.g., phenylaminoalkyl, di-phenwherein R is hydroxy, etc., hydrogen, aryl, e.g., phenyl, naphthyl, etc., lower alkyl having one to eight carbon atoms e.g., methyl, ethyl, propyl, etc., amino including substituted amino e.g., diloweralkylamino, lower alkoxy having one to eight carbon atoms e.g., butoxy, methoxy, etc., aryloxy, e.g., phenoxy, naphthoxy, etc.,

2. a cycloalkyl group having four to eight carbon atoms in the cyclic nucleus e.g., cyclobutyl, cyclohexyl, cyclopentyl, etc., including a substituted cycloalkyl group such as a. alkoxycycloalkyl e.g., ethoxycy'clohexyl, methoxycyclobutyl, propoxycyclohexyl, etc.,

b. aryloxycycloalkyl, e.g., phenoxycyclohexyl, naphthoxycyclohexyl, phenoxycyclopentyl, etc.,

0. aminocycloalkyl, e.g., aminocyclobutyl,

cyclohexyl, aminocyclopentyl, etc.,

d. hydroxycycloalkyl e.g., aminocyclohexyl, hydroxycyclopentyl, hydroxycyclobutyl, etc.,

e. arylcycloalkyl e.g., phenylcyclohexyl, phenylcyclobutyl, etc.,

f. alkylaminocycloalkyl e.g., methylaminocyclohexyl,

methylaminocyclopentyl, etc., and also including dialkylaminocycloalkyl e.g., diethylaminocyclohexyl, dimethylaminocyclobutyl, dipropylaminocyclooctyl, etc.,

g. arylaminocycloalkyl, e,g., phenylaminocyclohexy],

diphenylaminocyclohexyl, N-phenyl-N-ethylaminocyclopentyl, N-phenyl-N-methylaminocyclohexyl, naphthylaminocyclopentyl, etc.,

h. nitrocycloalkyl, e.g., nitrocyclobutyl, nitrocyclohexyl,

nitrocyclopentyl, etc.,

i. cyanocycloalkyl, e.g., cyanocyclohexyl, cyanocyclobutyl, cyanocyclopentyl, etc.,

j. halocycloalkyl e.g., chlorocyclohexyl, bromocyclopen' tyl, chlorocyclooc'tyl, etc.,

k. cycloalkyl substituted with an acyl group having the formula 1 aminowherein R is hydroxy, hydrogen, aryl e.g., phenyl, naphthyl, etc., amino including substituted amino e.g., diloweralkylamino, loweralkoxy having one to eight carbon atoms, e.g., butoxy, methoxy, etc., aryloxy e.g., phenoxy, naphthoxy; etc., lower alkyl having one to eight carbon atoms e.g., methyl, ethyl, propyl, butyl, etc., or

3. a hcterocyclic group including a substituted heterocyclic group containing fiveto six-members in the heteronucleus and including at least one sulfur, selenium, oxygen or nitrogen atom such as a thienyl group e.g., a benzothienyl group, a pyrrolyl group, eg, a nitropyrrolyl group, a pyrrolidinyl group e.g., a prolyl group, a pyrrolinyl group, a benzopyrrolyl group e.g., an indolyl group, a carbazolyl group, a furyl group e.g., a furfuryl group, a benzofuryl group etc., a pyridyl group, e.g., a halopyridyl group, an aminopyridyl group, a hydroxypyridyl group,

an alkylpyridyl group, a nitropyridyl group etc., a piperidyl group, a quinolyl group, an acridinyl group, a pyranyl group, a benzopyranyl group, a pyrazolyl group, an oxazolyl group, a thiazolyl group, etc.; or

4. an aryl group, e.g., phenyl, naphthyl, anthryl, fluorenyl,

etc., including a substituted aryl group such as a. alkoxyaryl, e.g., ethoxyphenyl, methoxyphenyl,

propoxynaphthyl, etc.,

b. aryloxyaryl, e.g., phenoxyphenyl, naphthoxyphenyl,

phenoxynaphthyl, etc.,

c. aminoaryl, e.g.,

aminoanthryl, etc.,

d. hydroxyaryl, e.g., hydroxyphenyl, hydroxynaphthyl,

hydroxyanthryl, etc.,

e. biphenylyl,

f. alkylaminoaryl, e.g., methylaminophenyl,

methylaminonaphthyl, etc., and also including dialkylaminoaryl, e.g., diethylaminophenyl, dipropylaminophenyl, etc.,

g. arylaminoaryl, e.g., phenylaminophenyl, diphenylaminophenyl, N-phenyl-N-ethylaminophenyl, N- phenyl-N-chloroaminophenyl, naphthylaminophenyl,

aminophenyl, aminonaphthyl,

etc.,

h. nitroaryl e.g,, nitrophenyl, nitronaphthyl, nitroanthryl,

etc.,

i cyanoaryl, e.g., cyanophenyl, cyanonaphthyl,

cyanoanthryl, etc.,

j. haloaryl, e.g., chlorophenyl, bromophenyl,

chloronaphthyl, etc., k. aryl substituted with an acyl group having the formula wherein R is hydroxy, hydrogen, aryl, e.g., phenyl, naphthyl, etc., amino including substituted amino, e.g., diloweralkylamino, lower alkoxy having 1 to 8 carbon atoms, e.g., butoxy, methoxy, etc., arloxy, e.g., phenoxy, naphthoxy, etc., lower alkyl having one to eight carbon atoms, e.g., methyl, ethyl, propyl, butyl, etc.,

1. alkaryl, e.g., totyl, ethylphenyl, propyl, naphthyl, etc.;

5. an unsaturated alkyl group having two to 18 carbon atoms (including substituted unsaturated alkyl groups) such as a. alkenyl e.g., vinylidene, propylidene, butyl-idene, etc.,

b. alkynyl e.g., ethynyl, l-propynyl, l-butynyl, l-isopentynyl,etc., c. alkadienyl e.g., butadienyl (1,3), pentadienyl (1,3),

etc.,

d. aralkenyl e.g., styryl, 3-phenylpropylidene, 4-phenylbutylidene, etc.,

e. aralkynyl e.g., phenethynyl, 3-phenylpropynyl, 4-phenylbutynyl, etc.,

f. aralkadienyl e.g., 4-phenyl-butadienyl (1,3), Spentadienyl (1,3), etc., or

g. hydrogen.

Z represents the nonmetallic atoms necessary to complete a heterocyclic nucleus containing five to six atoms in the heterocyclic ring, which nucleus can contain at least one additional hetero atom such as oxygen, sulfur, selenium or nitrogen, Le, a nucleus of the type used in the production of cyanine dyes, such as the following representative nuclei: a thiazole nucleus, e.g., thiazole,4methylthiazole, 3-ethylthiazole, 4-phenylthiazole, S-methylthiazole, S-phenylthiazole, 4,5- dimethylthiazole, 4,5-diphenylthiazole, 4-(2-thienyl)thiazole,

benzothiazole, 4-chlorobenzothiazole, 4- or 5- nitrobenzothiazole, S-chlorobenzothiazole, 6- chlorobenzothiazole, 7-chlorobenzothiazole, 4-methylbenzothiazole, S-methylbenzothiazole, 6-methylbenzothiazole, 6-nitrobenzothiazole, 5-bromobenzothiazole,

6-bromobenzothiazole,. 5-chloro-6-nitrobenzothiazole, 4- phenylbenzothiazole, 4-m ethoxybenzothiazole, S-methoxybenzothiazole, o-methoxybenzothiazole, 5-

iodobenzothiazole, (a-iodobenzothiazole, 4-ethoxybenzothiazole, 5 -ethoxybenzothiazole, a tetrahydrobenzothiazole nucleus, 5 ,6-dimethoxybenzothiazole, 5,6-methylenedioxybenzothiazole, S-hydroxybenzothiazole, o-hydroxybenzothiazole, a-naphthothiazole, B-naphthothiazole, B,B-naphthothiazole, S-methoxy-fiL/inaphtho-thiazole, 5-ethoxy-B-naphthothiazole, 8-methoxy-anaphthothiazole, 7-methoxy-a-naphthothiazole, 4 -methoxythianaphtheno-7',6',4,5-thiazole, 3-ethyl-2,3- dihydrothiazolo[4,5-b1quinoline, nitro group substituted naphthothiazoles, etc.; an oxazole nucleus, e.g., 4-methyloxazole, 4-nitrooxazole, S-methyloxazole, 4-phenyl-oxazole, 4,5-diphenyloxazole, 4-ethyloxazole, 4,5-dimethyloxazole, 5- phenyloxazole, benzoxazole, 5-chlorobenzoxazole, S-methylbenzoxazole, S-phenylbenzoxazole, 5- or -nitrobenzoxazole, 5-chloro-6-nitrobenzoxazole, o-methylbenzoxazole, 5,6- dimethylbenzoxazole, 4,6-dimethylbenzoxazole, S-methoxybenzoxazole, S-ethoxybenzoxazole, 5-chlorobenzoxazole, 6- methoxybenzoxazole, S-hydroxybenzoxazole, 6-hydroxybenzoxazole, a-naphthoxazole, B-naphthoxazole, nitro group substituted naphthoxazoles, etc.; a selenazole nucleus, e.g., 4- methylselenazole, 4-nitroselenazole, 4-phenylselenazole, benzoselenazole, 5-chlorobenzoselenazole, S-methoxybenzoselenazole, S-hydroxybenzoselenazole, 5- or 6- nitrobenzoselenazole, 5-chloro--nitrobenzoselenazole, tetrahydrobenzoselenazole, a-naphthoselenazole, B- naphthoselenazole, nitro group substituted naphthoselenazoles, etc.; a thiazoline nucleus, e.g., t'hiazoline, 4-methylthiazoline, etc.; a pyridine nucleus, e.g., Zpyridine, 5- methyI-Zpyridine, 4-pyridine, 3-methyl-4-pyridine, nitro group substituted pyridines, etc.; a quinoline nucleus, e.g., 2quinoline, 3-methyl-2quinoline, S-ethyl-Z-quinoline, 6- chloro-Zquinoline, 6-nitro-2-quinoline, 8-chloro-2-quinoline, 6-methoxy-2quinoline, 8-ethoxy-2-quinoline, 8-hydroxy-2- quinoline, 4-quinoline, 6-methoxy-4-quinoline, 6-nitro-4 quinoline, 7-methyl-4-quinoline, 8-chloro-4-quinoline, lisoquinoline, 6-nitrol -isoquinoline, 3,4-dihydro-1-isoquinoline, 3-isoquinoline, etc.; a 3,3-dialkylindolenine nucleus, preferably having a nitro or cyano substituent, e.g., 3,3- dimethyl-S or -nitroindolenine, 3,3'dimethyl-5- or 6- cyanoindolenine, etc.; an imidazole nucleus, e,g., imidazole, l-alkylimidazole, l-alkyl-4-phenylimidazole, l-alkyl-4,5- dimethylimidazole, benzimidazole, l-alkylbenzimidazole, lalkyl-S-nitrobenzimidazole, l-aryl-5,6- dichlorobenzimidazole, l-alkyl-a-naphthimidazole, l-aryl-B- naphthimidazole, l-alkyl-5-methoxy-a-naphthimidazole, or, an imidazoI4,5-b]quinoxaline nucleus, e.g., l-alkylimidazol4,5-blquinoxaline such as lethylimidazo-[4,5- blquinoxaline, 6-ehloro-l ,3-diethyl-2,3-dihydrol H-imidazo- [4,5'b]quinoxaline, 6-chloro-l-ethylimidazo[4,5-blquinoxaline, etc., l-alkenylimidazo[4,5-b1quinoxaline such as l-allylimidazo-[4,5-b ]quinoxaline, 1,3-diallyl-6-chloro-l ,2- dihydroimidazo[4,5-blquinoxaline, 6-chloro-l-allylimidazo[ 4,5-blquinoxaline, etc., 1-arylimidazo[4,5-blquinoxaline such as l-phenylimidazo[4,5-b]quinoxaline, 6-chloro-l-phenylimidazo[4,5bIquinoxaline, etc.; a 3,3-dialkyl-3H-pyrrolo[ 2,3-b]pyridine nucleus, e.g., 3,3-dimethyl-3H-pyrrolo[2,3- blpyridine, 3,3-diethyl-3H-pyrrolo[2,3-b]pyridine, 1,3,3- trimethyl-l,2-dihydro-3l-l-pyrrolo[2,3-b]pyridine, etc.; a thiazolo[4,5-b]quinoline nucleus; an indolyl nucleus including substituted indolyl nuclei such as a 2-phenyl-3-indole, lmethyl-2-phenyl-3-indole; and the like; n is a positive integer of l or 3.

Typical compounds which belong to the herein described general class of sensitizing dyes include the following:

dihydrothiazolol4,5-b1quinoline Vll Vlll

Xll

Xlll

XIV

Electrophotographic elements of the invention can be prepared with any photoconductive compound and the sensitizers of this invention in the usual manner, i.e., by blending a dispersion or solution of the photoconductive compound together with a binder, when necessary or desirable, and coating or forming a self-supporting layer with the photoconductive composition. Generally, a suitable amount of the sensitizing compound is mixed with the photoconductive coating composition so that, after thorough mixing, the sensitizing compound is uniformly distributed throughout the desired layer of the coated element. The amount of sensitizer that can be added to a photoconductor-incorporating layer to give ef fective increases in speed can vary widely. The optimum concentration in any given case will vary with the specific photoconductor and sensitizing compound used. In general, substantial speed gains can be obtained where an appropriate sensitizer is added in a concentration range from about 0.000] to about 30 percent by weight of the film-forming coating composition. Normally, a sensitizer is added to the coating composition in an amount from about 0.005 to about 5.0 percent by weight of the total coating composition.

The sensitizers of this invention improve the electrical speeds of compositions containing a wide variety of photoconductors, including inorganic photoconductors such as zinc oxide, titanium dioxide, cadmium sulfide and the like, organic photoconductors including organometallic photoconductors and mixtures thereof. Also, polymeric photoconductors can be used.

Typical additional photoconductors useful with the binders of this invention are described below.

A. Arylamine photoconductors including substituted and unsubstituted arylamines, diarylamines, nonpolymeric triarylamines and polymeric triarylamines such as those described in U.S. Pats. Nos. 3,240,597 and 3,180,730.

B. Photoconductors represented by the formula wherein Z represents a mononuclear or polynuclear divalent aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, binaphthyl, etc.), or a substituted divalent aromatic radical of these types wherein said substituent can comprise a member such as an acyl group having from one to about six carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkyl group having from one to about six carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc), an alkoxy group having from one to about six carbon atoms (e.g., methoxy, ethoxy,

propoxy, pentoxy, etc.), or a nitro group; Z represents a mononuclear or polynuclear monovalent aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, etc.); or a substituted monovalent aromatic radical wherein said substituent can comprise a member, such as an acyl group having from one to about six carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkyl group having from one to about six carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy' group having from one to about six carbons atoms (e.g., methoxy, propoxy, pentoxy, etc.), or a nitro group; O can represent a hydrogen atom or an aromatic amino group, such as ZNH; b represents an integer from one to about 12, and L represents a hydrogen atom, a mononuclear or polynuclear aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, etc.), a substituted aromatic radical wherein said substituent comprises an alkyl group, an alkoxy group, an acyl group, or a nitro group, or a poly(4-vinylphenyl) group which is bonded to the nitrogen atom by a carbon atom of the phenyl group, these materials being more fully described in U.S. Pat. No. 3,265,496.

C. Polyarylalkane photoconductors including leuco bases of diaryl or triarylmethane dye salts, 1,1 ,l-triarylalkanes wherein the alkane moiety has at least two carbon atoms and tetraarylmethanes having an amino group substituted in at least one of the aryl nuclei attached to the alkane and methane moieties of the latter two classes of photoconductors which are nonleuco base materials; and also other polyarylalkanes included by the formula:

wherein each of D, E and G is an aryl group and J is a hydrogen atom, an alkyl group, or an aryl group, at least one of D, E and G containing an amino substituent, the aryl groups attached to the central carbon atom being preferably phenyl groups, although naphthyl groups can also be used including substituted aryl groups containing substituents such as alkyl and alkoxy typically having one to eight carbon atoms, hydroxy, halogen, etc., in the ortho, meta or para positions, ortho-substituted phenyl being preferred; the aryl groups can also be joined together or cyclized to form a fluorene moiety, for example; the amino substituent can be represented by the formula wherein each R can be an alkyl group typically having one to eight carbon atoms, a hydrogen atom, an aryl group, or together the necessary atoms to form a heterocyclic amino group typically having five to six atoms in the ring such as morpholino, pyridyl, pyrryl, etc.; at least one of D, E and G preferably being a p-dialkylaminophenyl group, when J is an alkyl group, such an alkyl group more generally has one to seven carbon atoms, these materials being more fully described in U.S. Pat. No. 3,274,000, French Pat. No. 1,383,461 and in U.S. application, Ser. No. 627,857 filed Apr. 3, 1967 by Seus and Goldman, now U.S. Pat. No. 3,542,544.

D. Photoconductors comprising 4-diarylamino substituted chalcones having the formula:

wherein R and R are each phenyl radicals including substituted phenyl radicals, R preferably having the formula:

wherein R and R, are each aryl radicals, aliphatic residues of one to 12 carbon atoms such as alkyl radicals preferably having one to four carbon atoms, or hydrogen; particularly advantageous results being obtained when R is a phenyl radical including a substituted phenyl radical and where R is diphenylaminophenyl, dimethylaminophenyl or phenyl, these materials being more fully described in Fox U.S. application, Ser. No. 613,846, filed Feb. 3, 1967, now U.S. Pat. No. 3,526,501. E. Nonionic cycloheptenyl compounds which may be substituted with substituents such as:

1. an aryl radical including substituted as well as unsubstituted aryl radicals,

2. a hydroxy radical,

3. an azido radical,

4. a heterocyclic radical having five to six atoms in the heterocyclic nucleus and at least one hetero nitrogen atom, and including substituted and unsubstituted heterocyclic radicals, and

5. an oxygen linked cycloheptenyl moiety.

The substitution on the cycloheptenyl nucleus occurs at an unsaturated carbon atom when the cycloheptenyl moiety is a conjugated triene with no aromatic structure fused thereto. However, if there is at least one aromatic structure fused to the cycloheptenyl moiety, then the substituents are attached to a saturated carbon atom. Additional photoconductors within this class are included in one of the following formulas:

R u r 1 and Re- Ru where E and G can be either:

1. a phenyl radical,

2. a naphthyl radical,

3. a heterocyclic radical having five to six atoms in the heterocyclic nucleus and at least one hetero nitrogen atom,

4. a hydroxyl radical, or

5. an oxygen containing radical having a structure such that the resultant cycloheptenyl compound is a sym metrical ether; D can be any of the substituents defined for E and G above and is attached to a carbon atom in the cycloheptenyl nucleus having a double bond; (R and R (R and R (R and R and (R and R are together the necessary atoms to complete a benzene ring fused to the cycloheptenyl nucleus; these compounds being more fully described in US. application, Ser. No. 654,091 filed July 18, 1967, now U.S. Pat. No. 3,533,786.

F. Compounds containing an nucleus including:

1. unsubstituted and substituted N,N-bicarbazyls containing substituents in either or both carbazolyl nuclei such a. an alkyl radical including a substituted alkyl radical such as a haloalkyl or an alkoxyalkyl radical,

b. a phenyl radical including a substituted phenyl radical such as a naphthyl, an aminophenyl or a hydroxyphenyl radical,

c. a halogen atom,

d. an amino radical including substituted as well as unsubstituted amino radicals such as an alkylamino or a phenylalkylamino radical,

e. an alkoxy radical,

f. a hydroxyl radical,

g. a cyano radical,

h. a heterocyclic radical such as a pyrazolyl, carbazolyl or a pyridyl radical; or

2. tetra-substituted hydrazines containing substituents which are substituted or unsubstituted phenyl radicals, or heterocyclic radicals having five to six atoms in the hetero nucleus, suitable results being obtained when all four substituents are not unsubstituted phenyl radicals,

i.e., if at least one substituent is a substituted phenyl radical or a heterocyclic radical having five to six atoms in the hetero nucleus. Other tetra-substituted hydrazines include those having the following formula:

wherein D,, E,, G and J are each either:

a. a substituted phenyl radical such as a naphthyl radical, an alkyl phenyl radical, a halophenyl radical, a hydroxyphenyl radical, a haloalkylphenyl radical or a hydroxyalkylphenyl radical, or

b. a heterocyclic radical such as an imidazolyl radical, a furyl radical, or a pyrazolyl radical. In addition J and E, can also be c. an unsubstituted phenyl radical.

Especially preferred are those tetra-substituted hydrazines wherein both D and G are either substituted phenyl radicals or heterocyclic radicals. These compounds are more fully described in US. application, Ser, No. 673,962 filed Oct. 9, 1967, now US. Pat. No. 3,542,546.

G. Organic compounds having a 3,3-bis-aryl-2-pyrazoline nucleus which is substituted in either five-member ring with the same or different substituents. The oneand fivepositions on both pyrazoline rings can be substituted by an aryl moiety including unsubstituted as well as substituted aryl substituents such as alkoxyaryl, alkaryl, alkaminoaryl, carboxyaryl, hydroxyaryl and" haloaryl. The 4-position can contain hydrogen or unsubstituted as well as substituted alkyl and aryl radicals such as alkoxyaryl, alkaryl, alkaminoaryl, haloaryl, hydroxyaryl, alkoxyalkyl, aminoalkyl, carboxyaryl, hydroxyalkyl and haloalkyl. Other photoconductors in this class are represented by the following structure:

wherein:

D D J and J can be either a phenyl radical including a substituted phenyl radical such as a tolyl radical or a naphthyl radical including a substituted naphthyl radical, E E G 6;, L and L can be any of the substituents set forth above and in addition can be either a hydrogen atom or an alkyl radical containing one to eight carbon atoms. These organic photoconductors are more fully described in US. application, Ser. No. 664,642 filed Aug. 31, 1967, now US. Pat. No. 3,527,602.

H. Triarylamines in which at least one of the aryl radicals is substituted by either a vinyl radical or a vinylene radical having at least one active hydrogen-containing group. The phrase vinylene radical" includes substituted as well as unsubstituted vinylene radicals and also includes those radicals having at least one and as many as three repeat ing units of vinylene groups such as {CH=CH wherein n is an integer of from 1 to 3. Groups which contain active hydrogen are well known in the art, the definition of this term being set forth in several textbooks such as Advanced Organic Chemistry, R. C. Fuson, pp. 154-157, John Wiley & Sons 1950. The term active hydrogen-containing group as used herein includes those compounds encompassed by the discussion in the textbook cited above and in addition includes those compounds which contain groups which are hydrolyzable to active hydrogen-containing groups. Typical active hydrogen-containing groups substituted on the vinylene radical of the triarylamine include:

1. carboxy radicals, 2. hydroxy radicals, 3. ethynyl radicals,

4. ester radicals (e.g.,

wherein R is alkyl or aryl) including cyclic ester radicals (e.g.,

wherein R is a cyclic alkylene radical connected to a vinylene combination such as is found is coumarin derivatives),

5. carboxylic acid anhydride radicals,

semicarbazono radicals, cyano radicals,

6. 7. 8. acyl halide radicals 0 ii (e.g., -Cl, etc.), and

9. amido radicals wherein R is a hydrogen atom, an alkyl group or an aryl group). Other active hydrogen-containing groups include substituted and unsubstituted alkylidyne oximido radical s.

Photoconductors included in this class can be represented by the following structure:

Ar: Rn R11 n"-X wherein:

a. an active hydrogen-containing group such as a carboxy radical, an acyl halide radical, an amido radical, a carboxylic acid anhydride radical, an ester radical, a cyano radical, a hydroxy radical, a semicarbazono radical, an ethynyl radical, or a methylidyne oximido radical, or

b. hydrogen, provided that when X is hydrogen R and R are also hydrogen, and

5. n is an integer of l to 3. The arylene nucleus can be substituted in any position by the vinyl or vinylene moiety. However, when Ar; is phenylene, particularly good results are obtained if the substitution occurs in the para position. These materials are more fully described in U.S application, Ser. No. 706,800 filed Feb. 20, 1968, corresponding to Belgium Pat. No.

I. Triarylamines in which at least one of the aryl radicals is substituted by an active hydrogen-containing group. The term active hydrogen-containing group has the same meaning as set forth above and again includes those compounds encompassed by the discussion in the textbook and additionally includes those compounds which contain groups which are hydrolyzable to active hydrogen-containing groups. Typical active hydrogen-containing groups which are substituted on an aryl radical of the triarylamine include:

1. carboxy radicals, 2. hydroxy radicals, 3. ethynyl radicals, 4. ester radicals (e.g., -C R1 wherein R1! is an alkyl or an aryl group),

II (e.g., -C-C1, etc.),

10. amido radicals wherein Rn is a hydrogen atom, an alkyl group or an aryl group),

1 1. lower alkylidyne oximido radicals having one to eight carbon atoms including substituted alkylidyne oximido radicals (e.g., (IJ=NOH wherein Rzu R is hydrogen or a lower alkyl radical),

l2. semicarbazono radicals, and 13. arylene carboxy radicals including substituted arylene carboxy radicals wherein D and E are phenyl or lower alkyl radicals.

Photoconductors included in this class can be represented by the following structure:

wherein:

a. Ar and Ar are each a phenyl radical including a substituted phenyl radical such as a halophenyl radical,'an alkyl phenyl radical or an amino phenyl radical,

b. Ar is an arylene radical including a substituted arylene radical such as a phenylene radical or a naphthylene radical, and

c. X, is an active hydrogen-containing group such as a carboxy radical, an acyl halide radical, an amido radical, a carboxylic acid anhydride radical, an ester radical, a cyano radical, a semicarbazono radical, a hydroxy radical, an ethynyl radical, a methylidyne oximido radical or a phenylene carboxy radical.

These materials are more fully described in US. application, Ser. No. 706,780 filed Feb. 20, 1968.

J. Organometallic compounds having at least one aminoaryl substituent attached to a Group lVa or Group Va metal atom. The metallic substituents of this class of organic photoconductors are Group No or Group Va metals in accordance with the Periodic Table of the Elements (Handbook of Chemistry and Physics, 38th edition, pp. 394-) and include silicon, germanium, tin and lead from Group [Va and phosphorus, arsenic, antimony and bismuth from Group Va. These materials can be substituted in the metallo nucleus with a wide variety of substituents but at least one of the substituents must be an amino-aryl radical. The amino radical can be positioned anywhere on the aromatic nucleus, but best results are obtained if the aryl moiety is a phenyl radical having the amino group in the 4 or para position. Typical substituents attached to the metal nucleus include the followl. a hydrogen, sulfur or oxygen atom,

2. an alkyl radical,

3. an aryl radical including unsubstituted as well as substituted aryl radicals such as aminoaryl, alkylaryl and haloaryl,

4. an oxygen-containing radical such as an alkoxy or aryloxy radical,

5. an amino radical including unsubstituted and substituted amino radials such as monoand diarylamino and monoand dialkylamino radicals,

6. a heterocyclic radical, and

7. a Group lVa or Va organo metallic radical.

Photoconductors included in this class can be represented by the following structures:

where E G L and Q can be:

a. ahydrogen atom,

b. an aryl radical including unsubstituted as well as substituted aryl radicals such as a phenyl radical, a naphthyl radical, a dialkylaminophenyl radical, or a diarylaminophenyl radical,

c. an alkyl radical having one to eight carbon atoms,

d. an alkoxy radical having one to eight carbon atoms,

e. an aryloxy radical such as a phenoxy radical,

f. an amino radical having the formula wherein R and R can be hydrogen atoms or alkyl radicals having one to eight carbon atoms, or

g. a heterocyclic radical having five to six atoms in the hetero nucleus including at least one nitrogen atom such as a triazolyl, a pyridyl radical, etc.,

T is an amino radical such as an alkylamino radical having 1 to 8 carbon atoms or an arylamino radical such as a phenylamino radical; AR is an aromatic radical such as phenyl or naphthyl;

M and M are the same or different Group lVa metals;

M is a Group Va metal;

D can be any of the substituents set forth above for E G L and Q and in addition can be a Group N11 organometallic radical or, when taken with E, an oxygen atom or a sulfur atom;

.l can be any of the substituents set forth above for E G L and Q and in addition can be when taken with E, an oxygen atom or a sulfur atom. These materials are described in US. application Ser. No. 650,664 filed July 3, i967, corresponding to Canadian Pat, No. 818,5 39.

K. Any other organic compound which exhibits photoconductive properties such as those set forth in Australian Pat. No. 248,402.

Representative organic photoconductors useful in this invention include the compounds listed below:

TABLE I diphenylamine dinaphthylamine N,N '-diphenylbenzidine N-phenyll -naphthylamine N-phenyl-Z-naphthylamine N ,N'-diphenyl-p-phenylenediamine 2-carboxy-5-chloro-4 '-methoxydiphenylamine p-anilinophenol N ,N -di-2-naphthyl-p-phenylenediaminc 4,4'-benzylidene-bis-( N,N-dimethyl-m-toluidine) triphenylamine N ,N,N ,N -tetraphenyl-m-phenylenediamine 4-acetyltriphenylamine 4-hexanoyltriphenylamine 4-lauroyltriphenylamine 4-hexyltriphenylamine 4-dodecyltriphenylamine 4,4-bis(diphenylamino )benzil 4,4-bis(diphenylamino )benzophenone poly[ N ,4 -(N,N ,N '-triphenylbenzidine polyadipyltriphenylamine polysebacyltriphenylamine polydecamethylcnetriphenylamine poly-N-(4-vinylphenyl )diphenylamine poly-N-(vinylphenyl)-a, a'dinaphthylamine 4,4 -benzylidene-bis( N,N-diethyl-m-toluidine) 4 ',4' '-diamino-4-dimethylamino-2 ,2 dimethyltriphenylmethane 4,4"-bis(diethylamino)-2,6-dichloro-2,2-dimethyltriphenylmethane 4,4"-bis(diethylamino)-2,2"-dimethyldiphenylnaphthylmethane 2',2"-dimethyl-4,4,4"-tris(dimethylamino)triphenylmetha 4',4-bis(diethylamino)-4-dimethylamino-2,2"-dimethyltriphenylmethane 4',4"-bis(diethylamino)-2-chloro-2',2"-dimethyl-4- dimethylaminotriphenylmethane 4',4"-bis(diethylamino)-4-dimethylamino-2,2',2"-

trimethyltriphenylmethane 4',4"-bis(dimethylamino)-2-chloro-2',2"-dimethyltriphenylmethane 4',4"-bis(dimethylamino)-2',2"-dimethyl-4-methoxytriphenylmethane bis(4-diethylamino)- l ,l l -triphenylethane bis(4-diethylamino)tetraphenylmethane 4',4"-bis(benzylethylamino)-2',2"-dimethyltriphenylmethane 4',4"-bis( diethylamino)-2',2"-diethoxytriphenylmethane 4,4 '-bis( dimethylamino)- l l l -triphenylethane l-(4-N,N-dimethylaminophenyl)-l ,l-diphenylethane 4-dimethylaminotetraphenylmethane 4-diethylaminotetraphenylmethane 4,4'-bis(diphenylamino)chalcone 4-diphenylamino-4'-dimethylaminochalcone 4-dimethylamino-4'-diphenylaminochalcone 4,4'-bis(dimethylamin0)chalcone 4,4 '-bis(diethylamino)chalcone 4-diethylamino-4'-diphenylaminochalcone 4'diphenylaminochalcone 4-dimethylaminochalcone 4-diphenylaminochalcone 4'-dimethylaminochalcone bis-[5-dibenzo[a,dlcycloheptenyl)]ether 1- {5-(5H-dibenzo[a,dlcycloheptenyl)}-4,S-dicarbomethoxyl ,2,3-triazole l- {S-(SH-dibenzol a,d]cyclohepteny] -4,5-dibenzoyll,2,3-triazole 5-azid0-5H-dibenzo[a,d lcycloheptene l-{5-( 10,1 l-dihydro-5H-dibenzola,d]cycloheptenyl)} -4,5-

dicarbomethoxyl ,2,3-triazole 4-[5H-dibenzo[ a,d]cycloheptenyl)]-N,N-dimethyl aniline N,N-diethyl-3-methyl-4-[ 5-( 5H-dibenzo[ a,d]cyclohepteny l)]aniline 4-[5-(5H-dibenzo[a,d]cycloheptenylfll dimethylaminonaphthalene N,N-diethyl-3-methyl-4-[ 5-( l0,] l-dihydro-SH- dibenzo[a,d]cycloheptenyl)]aniline 3-(4-dimethylaminophenyl l ,3 ,S-cycloheptatriene 3-(4-diethylamino-2-methylphenyl)-1,3,5-cycloheptatriene 3-(4-dimethylaminonaphthyl)-l,3,5-cycloheptatriene N,N-diethyl-3-methyl-4-[ 5-(5l-l-dibenzola,d]cyclohepteny l)]aniline tetra-a-naphthylhydrazine tetra(3-methyl-4-hydroxyphenyl)hydrazine tetra(m-hydroxyethylphenyl)hydrazine tetra(Z-methyl-S-chloroethylphenyl)hydrazine tetra( Z-methyl-S -hydroxyphenyl )hydrazine tetra( l-imidazolyl )hydrazine N,N-di-a-naphthyl-N,N'-di(3-methyl-4-hydroxyphenyl) hydrazine N-3-furyl-N-( 2-methyl-4-hydroxyphenyl )-N ,N '-di-B- naphthylhydrazine tetra-Bnaphthlhydrazine N,N -di-B-naphthyl-N,N -diphenylhydrazine tetra'4-tolylhydrazine N,N-diphenyl-N,N '-di( 3-methyl-4-hydroxyphenyl) hydrazine N,N-diphenyl-N,N'-di-p-chlorophenyl hydrazine phenyltri-( Z-methyl-S-hydroxyphenyl )hydrazine N ,N '-bicarbazyl cyclotetrakis( 3 ,9-carbazolylene) I 6-( 3-carbazolyl )-cyclotetrakis( 3 ,9-carbazolylene) 6-( 9-carbazolyl )-cyclotetrakis( 3 ,9--carbazolylene) 3,3 '-bis( 3-carbazolyl )-9,9 -bicarbazolyl 3-( 3-carbazolyl)-9-(9-carbazolyl)carbazole 3-(9-carbazolyl)-9'-bicarbazolyl 3,3 '-diethyl-9,9-bicarbazolyl 3,3-diphenyl-9,9-bicarbazolyl 3,3-dichloro-9,9'-bicarbazolyl 4,4-bis(diethylamino)-9,9'-bicarbazolyl 3,3'-diethoxy-9,9'-bicarbazolyl l ,1 '-dihydroxy-9,9'-bicarbazolyl 2,2'-dicyano-9,9-bicarbazolyl tetra(p-diethylaminophenyl)hydrazine 3,3'-bis(1,S-diphenyl-Z-pyrazoline) 3,3-bis( 1-p-tolyl-5-phenyl-2-pyrazoline) 3,3'-bis( l ,5-[ l-naphthyl1-2-pyrazoline 3,3'-bis( l ,5-diphenyl-4,S-dimethyl-Z-pyrazoline) 3,3'-bis( l ,4,5-triphenyl-2-pyrazoline) 3,3 '-bis( 1 ,5-di-p-tolyl-4-methoxy-2-pyrazoline) 3,3-bis( 1,5-diphenyl-4-dimethylamino-2-pyrazoline) 3,3'-bis[ l ,5-diphenyl-4-(p-chlorophenyl)-2-pyra2oline] 3,3 '-bis[ 1 ,5-diphenyl-4,5-di-(p-diethylaminophenyl)-2- pyrazoline] 3,3-bis[ l ,5-diphenyl-4-(p-methoxyphenyl)-5 -ethyl-2- pyrazoline] 3,3'-bis( l ,S-diphenyl-4chloromethyl-2-pyrazoline) l,5-diphenyl-4,5-dimethyl-3-[3 l -p-tolyl-4-diethyl-5' ,5'-methylphenyl )-2'-pyrazolyl]-2-pyrazoline 4-(p-diphenylaminophenyl)-3-butenl -yne p-diphenylaminostyrene ethyl p-diphenylaminocinnamate methyl p-diphenylaminocinnamate p-diphenylaminocinnamoyl chloride p-diphenylaminocinnamic acid N,N-diphenylamide p-diphenylaminocinnamic acid anhydride B-(p-diphenylaminophenyl)-2-butenoic acid bis(p-diphenylaminobenzal)succinic acid 4-N,N-bis(p-bromophenyl)aminocinnamic acid 1-( 4-diphenylamino )naphthacrylic acid p-diphenylaminocinnamic acid p-diphenylaminocinnamonitrile 7-diphenylamino coumarin p-diphenylaminophenylvinylacrylic acid p-diphenylaminobenzyl p'-diphenylaminocinnamate 7-( p-diphenylaminostyryl)coumarin p-diphenylaminocinnamyl alcohol 4-diphenylaminocinnamaldehyde semicarbazone O-p-diphenylaminocinnamoyl p'-diphenylaminobenzaldehyde oxime p-diphenylaminocinnamaldeyde oxime l,3-bis( p-diphenylaminophenyl)-2-propen- 1 -ol methyl p-diphenylarninobenzoate N,N-diphenylanthranilic acid 3-p-diphenylaminophenyll -propanol 4-acetyltriphenylamine semicarbazone ethyl 2,6-diphenyl-4 (p-diphenylaminophenyl)benzoate l-(p-diphenylaminophenyl)-l-hydroxy-3-butyne 4-hydroxymethyltriphenylamine l-( p-diphenylaminophenyl )eth anol 4-hydroxytriphenylamine Z-hydroxytriphenylamine 4-formyltriphenylamine oxime 4-acetyltriphenylamine oxime l-(p-diphenylaminophenyl )hexanol l-(p-diphenylaminophenyl)dodecanol p-diphenylaminobenzoic acid anhydride 4-cyanotriphenylamine p-diphenylaminobenzoic acid N,N-diphenylamide p-diphenylaminobenzoic acid p-diphenylaminobenzoyl chloride 3-p-diphenylaminophenylpropionic acid 4-formyltriphenylamine semicarbazone triphenyl-p-diethylaminophenylsilane methyl-diphenyl-p-diethylaminophenylsilane triphenyl-p-diethylaminophenylgermane triphenyl-p-dimethylaminophenylstannane triphenyl-p-diethylaminophenylstannane diphenyl-di-(p-diethylaminopheny] )stannane triphenyl-p-diethylaminophenylplumbane tetra-p-diethylaminophenylplumbane phenyl-di-(p-diethylaminophcnyl)phosphine bis(p-diethylaminophenyl)phosphine oxide tri-p-dimethylaminophenylarsine tri-p-diethylaminophenylarsine 2-methyl-4-dimethylaminophenylarsine oxide tri-p-diethylaminophenylbismuthine methyl-di-( p-diethylaminophenyl )arsine methyl-di-(p-diethylaminophenyl)phosphine phenyl-tri(p-diethylaminophenyl)stannane methyl-tri(p-diethylaminophenyl)stannane tetra-p-diethylaminophenylgermane diphenyl-p-diethylaminophenylsilane p-diethylaminophenylarsine tetrakis-[ diphenyl-( p-diethylaminophenyl )plumbyl] methane tetrakis-[ diphenyl-( p-diethylaminophenyl )stannyl stannane bis-[phenyl(p-diethylaminophenyl)]dibismuthine tri(p-diethylaminophenyl)phosphine sulfide di-(p-diethylaminophenyl)thioxotin Preferred binders for use in preparing the present photoconductive layers are film-forming, polymeric binders having fairly high dielectric strength which are good electrically insulating film-forming vehicles. Materials of this type comprise styrene-butadiene copolymers; silicone resins; styrene-alkyd resins; silicone-alkyd resins; soya-alkyd resins; poly(vinyl chloride); poly(vinylidene chloride); vinylidene chloride-acrylonitrile copolymers; poly(vinyl acetate); vinyl acetate-vinyl chloride copolymers; poly(vinyl acetals), such as poly(vinyl butyral); polyacrylic and methacrylic esters, such as poly(methy methacrylate), poly(n-butyl methacrylate), poly(isobuty] methacrylate), etc.; polystyrene; nitrated polystrene; polymethylstyrene; isobutylene polymers; polyesters, such as copoly[ethylene-co-alkylenebis(alkyleneoxyaryl)phenylenedicarboxylate]; phenolforrnaldehyde resins; ketone resins; polyamides; polycarbonates; polythiocarbonates; poly[ethylene-co-isopropylidene-2,2-bis(ethyleneoxyphenyl)terephthalate]; copolymers of vinyl haloarylates and vinyl acetate such as poly(vinyl m-bromobenzoate-co vinyl acetate); etc. Methods of making resins of this type have been described in the prior art, for example, styrene-alkyd resins can be prepared according to the method described in US. Pat. Nos. 2,361,019 and 2,258,423. Suitable resins of the type contemplated for use in the photoconductive layers of the invention are sold under such tradenames as Vitel PE-lOl, Cymac, Piccopale 100, Saran. F220, Lexan and Lexan 145. Other types of binders which .can be used in the photoconductive layers of the invention include such materials as paraffin, mineral waxes, etc. Also, mixtures of these binders can be used.

Solvents useful for preparing coating compositions with the photoconductors of the present invention can include a wide variety of organic solvents for the components of the coating composition. For example, benzene; toluene; acetone; 2-butanone; chlorinated hydrocarbons such as methylene chloride; ethylene chloride; and the like; others, such as tetrahydrofuran and the like or mixtures of such solvents can advantageously be employed in the practice of this invention.

In preparing the coating compositions useful results are obtained where the photoconductor substance is an amount equal to at least about 1 weight percent of the coating composition. The upper limitinthe amount of photoconductor substance present can be widely varied'in accordance with usual practice, In those cases where a binder is employed, it is normally required that the photoconductor substance be present in an amount from about 1 weight percent of the coating composition to about 99 weight percent of the coating composition. A preferred weight range for the photoconductor substance in the coating composition is from about weight percent to about 60 weight percent.

Coating thicknesses of the photoconductive composition on a support can vary widely. Normally, a coating in the range of about 0.001 inch to about 0.01 inch before drying is useful for the practice of this invention. The preferred range of coating thickness was found to be in the range from about 0.002 inch to about 0.006 inch before drying although useful results can be obtained outside of this range.

Suitable supporting materials for the photoconductive layers of the present invention can include any of a wide variety of electrically conducting supports, for example, various conducting papers; aluminum-paper laminates; metal foils such as aluminum foil, zinc foil, etc.; metal plates, such as aluminum, copper, zinc, brass, and galvanized plates; vapor deposited metal layers such as silver, nickel or aluminum on conventional film supports such as cellulose acetate, poly(ethylene terephthalate), polystyrene and the like conducting supports. An especially useful conducting support can be prepared by coating a support material such as poly(ethylene terephthalate) with a layer containing a semiconductor dispersed in a resin. Such conducting layers both with and without insulating barrier layers are described in US. Pat. No. 3,245,833. Likewise, a suitable conducting coating can be prepared from the sodium salt of a carboxyester lactone of a maleic anhydride-vinyl acetate copolymer. Such kinds of conducting layers and methods for their optimum preparation and use are disclosed in US. Pat. Nos. 3,007,901, 3,245,833 and 3,267,807.

The elements of the present invention can be employed in any of the well-known electrophotographic processes which require photoconductive layers. One such process is the aforementioned xerographic process. As explained previously, in a process of this type the electrophotographic element is given a blanket electrostatic charge by placing the same under a corona discharge which serves to give a uniform charge to the surface of the photoconductive layer. This charge is retained by the layer owing to the substantial insulating property of the layer, i.e., the low conductivity of the layer in the dark. The electrostatic charge formed on the surface of the photoconducting layer is then selectively dissipated from the surface of the layer by exposure to light through an image-bearing transparency by a conventional exposure operation such as, for example, by contact-printing technique, or by lens projection of an image, etc., to form a charge image in the photoconducting layer. By exposure of the surface in this manner, a charge pattern is created by virtueof the fact that light causes the charge to be conducted away in proportion to the intensity of the illumination in a particular area. The charge pattern remaining after exposure is then developed, i.e., rendered visible, by treatment with a medium comprising electrostatically attractable particles having optical density. The developing electrostatically attractable particles can be in the form of a dust, e.g., powder, a pigment in a resinous carrier, i.e., toner, or a liquid developer may be used in which the developing particles are carried in an electrically insulating liquid carrier. Methods of development of this type are widely known and have been described in the patent literature in such patents, for example, as US. Pat. No. 2,297,691, and in Australian Pat. No. 212,315. In processes of electrophotographic reproduction such as in xerography, by selecting a developing particle which has as one of its components, a low-melting resin, it is possible to treat the developed photoconductive material with heat and cause the powder to adhere permanently to the surface of the photoconductive layer. After development the visual contrast of the developed image is improved by exposure to light as described above.

The present invention is not limited to any particular mode of use of the new electrophotographic materials, and the exposure technique, the charging method, the transfer (if any), the

developing method, and the fixing method as well as the material used in these methods can be selected and adapted to the requirements of any particular technique.

Electrophotographic materials according to the present invention can be applied to reproduction techniques wherein different kinds of radiation, i.e., electromagnetic radiations as well as nuclear radiations can be used. For this reason, it is pointed out herein that although materials according to the invention are mainly intended for use in connection with methods comprising an exposure, the term electrophotography wherever appearing in the description and the claims, is to be interpreted broadly and understood to comprise both xerography and xeroradiography.

The following examples are set forth for a further understanding of the invention.

Example 1 A composition in the form of a dope consisting of the following materials is coated at a wet thickness of 0.004 inch on a poly(ethylene terephthalate) film support having a conducting layer of the sodium salt of butyl ester lactone made from a vinyl acetate-maleic anhydride copolymer as in Example 1 of US. Pat. No. 3,260,706;

Photoconductor 4,4'-benzylidenebis(N,N-diethyl-mtoluidine) 0.5 g. Binder poly(4,4-isopropylidene-bisphenyleneoxycthylene-coethylene terephthalate) l.5 g. Sensitizerl 0.02 g. Dichloromethane 9.60 g.

In a darkened room, the surface of the photoconductive layer so prepared is charged to a potential of about +600 volts under a corona charger. The layer is then covered with a transparent sheet bearing a pattern of opaque and light-transmitting area and exposed to the radiation from an incandescent lamp with an illumination intensity of about 75 metercandles for 12 seconds. The resulting electrostatic charge image is developed by cascading over the surface of the layer negatively charged black thermoplastic toner particles on glass bead carriers. The background area of the reproduction is highly colored and is very difficult to view. The developed image bearing element is then exposed to the radiation from a 500 watt G.E. lamp (Number PH/RFL2) at a distance of ten inches for 25 seconds. The background color is bleached to a pale yellow and the developed image has a substantially improved visual contrast.

Example 2 Several other sensitizing dyes are used in electrophotographic elements prepared in the manner described in Example 1. After exposure and development, the background area of each of the elements is of substantial coloration making the image portions difficult to view. The elements are then exposed to a 500watt source at a distance of 10 inches for the times set forth in the following Table. At the end of the exposure period substantially all of the background coloration is removed. Photoconductor A in the following Table is triphenylamine while Photoconductor B is the one employed in Example 1.

Example 3 Example 1 is repeated except the photoconductive coating composition contains the following:

Photoconductor bist t diethylamino)tetraphenylmethane- 0.5 g. Binder poly(vinyl-m-bromobenzoate-co-vinylacetate) L g. Sensitizerl 0.005 g. Solvent Dichloromethanc ll.7 ml.

After charging the element and exposing, the charge image is developed with a xerographic liquid developer. The resultant image is of very low contrast due to substantial coloration in background areas. The element is then bleached by subjecting it to a SOO-watt light source for 25 seconds at a distance of inches. The coloration in the background areas is virtually totally removed and the contrast is greatly improved.

Example 4 Example 3 is repeated except the sensitizer is omitted. No developable electrostatic charge image is obtained.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scope of the invention.

lclaim:

1. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising a photoconductor and as a sensitizer a dinitrophenylmethine dye terminated by a 5- to 6-membered heterocyclic nucleus of the type used in cyanine dyes containing at least one nitrogen atom.

2. The element of claim 1 wherein the photoconductor is an organic photoconductor.

3. The element of claim 1 wherein the photoconductive composition contains a polymeric film-forming binder.

4. An electrophotographic element comprising a support having coated thereon a photoconductive composition comprising an organic photoconductor and a sensitizer for said photoconductive composition having the formula:

wherein R is selected from the group consisting of hydrogen, an alkyl group, an alkenyl group, an aryl group and a heterocyelic group having five to six atoms in the hetero nucleus including at least one atom selected from the group consisting of sulfur, selenium, oxygen, and nitrogen,

Z represents the atoms necessary to complete a 5- to 6- membered heterocyclic nucleus, which nucleus includes at least one atom selected from the group consisting of sulfur, selenium, oxygen, and nitrogen, and

n is an integer of l or 3.

5. The element of claim 4 wherein the photoconductive composition contains a polymeric film-forming binder.

6. The element of claim 4 wherein Z represents the atoms necessary to complete a thiazole nucleus.

7. The element of claim 4 wherein 2 represents the atoms necessary to complete an imidazo nucleus.

8. The element of claim 4 wherein Z represents the atoms necessary to complete a pyrrolo[2,3-b]pyridine nucleus.

9. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising:

a. from about 10 percent to about 60 percent by weight based on said photoconductive composition of an organic photoconductor,

b. a film-forming polymeric binder for said photoconductor and c. 0.005% to about 5% by weight based on said photoconductive composition of a sensitizer comprising 2(2.4- dinitrobenzylidene)-3-ethyl-2,3-dihydrothiazolo[4,5- ]quinoline.

10. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising: i

a. from about 10 percent to about 60 percent by weight based on said photoconductive composition of an organic photoconductor,

b. a film-forming polymeric binder for said photoconductor and c. 0.005 percent to about 5 percent by weight based on said photoconductive composition of a sensitizer comprising l,3-diallyl-6-ehloro-2-( 2,4dinitrobenzylidene)- l ,2- dihydroimidazol4,5-bl-quinoxaline.

ll. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising:

a. from about 10 percent to about 60 percent by weight based on said photoconductive composition of an organic photoconductor,

b. a film-forming polymeric binder for said photoconductor and c. 0.005 percent to about 5 percent by weight based on said photoconductive composition of a sensitizer comprising 6-chloro-2-(2,4-dinitrobenzylidene)-l .3-diethyl-2.3- dihydro-lH-imidazol4,5-bl-quinoxaline.

12. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composi-- tion comprising:

a. from about l0 percent to about 60 percent by weight based on said photoconductive composition of an organic .photoconductor,

b. a film-forming polymeric binder for said photoconductor and c. 0.005% to about 5% by weight based on said photoconductive composition of a sensitizer comprising 2-(2,4- dinitrobenzylidenc)-l ,3-diethyll ,2-dihydroimidazol4,5- b]quinoxaline.

13. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising:

a. from about 10 percent to about 60 percent by weight based on said photoconductive composition of an organic photoconductor,

b. a film-forming polymeric binder for said photoconductor and c. 0.005 percent to about 5 percent by weight based on said photoconductive composition of a sensitizer comprising 2-(2,4-dinitrobenzylidene)-1,3,3-trimethyl-l ,2-dihydro- 3H-pyrrolol2,3-bl-pyridine.

14. A photoconductive composition comprising a photoconductor and as a sensitizer a dinitrophenylmethine dye terminated by a 5 to 6 membered heterocyclic nucleus of the type used in cyanine dyes containing at least one nitrogen atom.

15. The composition of claim 14 wherein the photoconductor is an organic compound.

16. The composition of claim 14 further comprising a polymeric film-forming binder.

17. A process for bleaching an image-bearing electrophotographic element having a layer ofa photoconductive composition containing as a sensitizer a dinitrophenylmethine dye ter-- minated by a 5- to 6-membered heterocyclic nucleus of the type used in cyanine dyes containing at least one nitrogen atom, said process comprising the step of subjecting the element to actinic radiation to which said dye is sensitive to substantially bleach said dye.

Disclaimer 3,647,433.-Lawren0e Edward Contoz's, WVebster, N.Y. DINITROARYL- METHINE DYES ASSENSITIZERS IN ELECTROPHOTO- GRAPHIC LAYERS. Patent dated Mar. 7 1972. Disclaimer filed Feb. 13, 1974, by the assignee, Eastman Kodak Company.

Hereby enters this disclaimer to all claims of said patent.

[Oyfioial Gazette August. 2'7, 1.974.]

UNITED STATES PATENT OFFICE PO-105O CERTIFICATE ()F ECTIUN Patent No 3 a 7 v v Dated March 7 1972 Lawrence E Contois Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 20 line 9 l7quinol ine should read yquinoline.

Signed and sealed this 19th day of September 1972.

(SEAL) Attest:

EDWARD MELETCHERJJR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

2. The element of claim 1 wherein the photoconductor is an organic photoconductor.
 3. The element of claim 1 wherein the photoconductive composition contains a polymeric film-forming binder.
 4. An electrophotographic element comprising a support having coated thereon a photoconductive composition comprising an organic photoconductor and a sensitizer for said photoconductive composition having the formula:
 5. The element of claim 4 wherein the photoconductive composition contains a polymeric film-forming binder.
 6. The element of claim 4 wherein Z represents the atoms necessary to complete a thiazole nucleus.
 7. The element of claim 4 wherein Z represents the atoms necessary to complete an imidazo nucleus.
 8. The element of claim 4 wherein Z represents the atoms necessary to complete a pyrrolo(2,3-b)pyridine nucleus.
 9. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising: a. from about 10 percent to about 60 percent by weight based on said photoconductive composition of an organic photoconductor, b. a film-forming polymeric binder for said photoconductor and c. 0.005% to about 5% by weight based on said photoconductive composition of a sensitizer comprising 2-(2,4-dinitrobenzylidene)-3-ethyl-2,3-dihydrothiazolo(4,5-)quinoline.
 10. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising: a. from about 10 percent to about 60 percent by weight based on said photoconductive composition of an organic photoconductor, b. a film-forming polymeric binder for said photoconductor and c. 0.005 percent to about 5 percent by weight based on said photoconductive composition of a sensitizer comprising 1,3-diallyl-6-chloro-2-(2,4-dinitrobenzylidene)-1,2-dihydroimidazo(4,5-b) -quinoxaline.
 11. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising: a. from about 10 percent to about 60 percent by weight based on said photoconductive composition of an organic photoconductor, b. a film-forming polymeric binder for said photoconductor and c. 0.005 percent to about 5 percent by weight based on said photoconductive composition of a sensitizer comprising 6-chloro-2-(2,4-dinitrobenzylidene)-1,3-diethyl-2,3-dihydro-1H-imidazo(4,5 -b)-quinoxaline.
 12. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising: a. from about 10 percent to about 60 percent by weight based on said photoconductive composition of an organic photoconductor, b. a film-forming polymeric binder for said photoconductor and c. 0.005% to about 5% by weight based on said photoconductive composition of a sensitizer comprising 2-(2,4-dinitrobenzylidene)-1,3-diethyl-1,2-dihydroimidazo(4,5-b)quinoxaline.
 13. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising: a. from about 10 percent to about 60 percent by weight based on said photoconductive composition of an organic photoconductor, b. a film-forming polymeric binder for said photoconductor and c. 0.005 percent to about 5 percent by weight based on said photoconductive composition of a sensitizer comprising 2-(2,4-dinitrobenzylidene)-1,3,3-trimethyl-1,2-dihydro-3H-pyrrolo(2,3-b) -pyridine.
 14. A photoconductive composition comprising a photoconductor and as a sensitizer a dinitrophenylmethine dye terminated by a 5 to 6 membered heterocyclic nucleus of the type used in cyanine dyes containing at least one nitrogen atom.
 15. The composition of claim 14 wherein the photoconductor is an organic compound.
 16. The composition of claim 14 further comprising a polymeric film-forming binder.
 17. A process for bleaching an image-bearing electrophotographic element having a layer of a photoconductive composition containing as a sensitizer a dinitrophenylmethine dye terminated by a 5- to 6-membered heterocyclic nucleus of the type used in cyanine dyes containing at least one nitrogen atom, said process comprising the step of subjecting the element to actinic radiation to which said dye is sensitive tO substantially bleach said dye. 